It is well known in the pharmaceutical art to apply a pharmaceutically active material to a smooth, spherical core. Typically, the process involves the application of a solution, suspension, or powder coating of the spherical core with the pharmaceutically active ingredient.
For example, Jones, D. M., in the chapter entitled, Solution and Suspension Layering, Pharmaceutical Pelletization Technology, describes layering a solution of drug onto seed material, generally a coarse crystal or nonpareil, in coating pans or fluidized bed equipment. The chapter notes that the Wurster process can be used for coating and layering onto substrates as small as 100 microns, and coated layers of 100 to 150% of the starting batch weight may be applied. The author also notes that a binder is optional, but recommended, when applying drug from a solution.
Despite the teachings of the prior art, it is highly desirable to apply a pharmaceutically active material via solution coating that does not require a separate granulation step in order to increase the size of the substrate core prior to coating.